Field of the Invention
The present invention relates to a telescopic cover for use as a movable cover of a machine tool.
Description of the Related Art
In a machine tool, sliding surfaces and drive parts, such as ball screws, are expected to be protected from chips and cutting fluid. Moreover, a movable cover generally called a telescopic cover that extends and retracts during axial movement is used in order to restrict the size of the machine tool. This telescopic cover or a movable cover is configured so that a plurality of cover pieces of different sizes are stacked in a nested fashion in the order of their size such that the entire structure can extend and retract in the inserting direction of the cover pieces.
As a widely used mechanism for extending and retracting the telescopic cover, there is a mechanism that uses, for example, a pantograph to extend and retract the cover in synchronism with machine movement by a feed axis (see Japanese Patent Application Laid-Open No. 2009-184026). Moreover, there is another known telescopic cover that is configured so that wipers are disposed on the distal end portions of the cover pieces of the telescopic cover to prevent penetration of chips, dust, cutting fluid and the like into a gap between the cover pieces (see Japanese Patent Applications Laid-Open Nos. 2009-184026 and 7-60593).
Further, there is a known technique in which a stopper is provided on a cover piece of a telescopic cover to restrict the stroke of the cover piece, thereby suppressing extension and retraction of the telescopic cover (see Japanese Patent Application Laid-Open No. 63-176045). As a means for limiting the extension and retraction of the telescopic cover, an extension/retraction suppressing mechanism is generally constructed such that a stopper is provided on one of cover pieces on the insert side (accommodated side) and the inset receiving side (accommodating side) and a buffer member such as a rubber cushion is provided on the other cover piece.
FIGS. 3A and 3B are views showing an example of the extension/retraction limiting mechanism of a conventionally used telescopic cover. In this example, the extension/retraction suppressing mechanism is formed by stoppers and rubber cushions provided on the cover pieces of a telescopic cover 1. This telescopic cover 1 comprises a first cover piece 10a, a second cover piece 10b that serves as an insert to be received in the first cover piece 10a, and a third cover piece 10c that serves as an insert to be received in the second cover piece 10b. FIG. 3A is a front view showing a state in which the telescopic cover 1 is retracted to its minimum length, and FIG. 1B is a front view showing a state in which the telescopic cover 1 is extended to its maximum length.
One of rubber cushions 11 is mounted on the inside surface of the top plate of the receiving-side cover piece receiving the insert-side cover piece, and a stopper 12 and a wiper 13 are provided on the outside surface of the upper surface of the receiving side thereof to receive the cover piece as the insert. In FIGS. 3A and 3B, the rubber cushions 11 are individually mounted inside the cover piece top plate at the left ends (insert-side cover piece accommodating ends) of the first and second receiving-side cover pieces 10a and 10b, and moreover, wipers 13 are provided on the upper surface ends of the cover pieces. The stoppers 12 are individually provided outside the cover piece top plate at the right ends (the end facing the receiving-side cover piece) of the second and third insert-side cover pieces 10b and 10c. Consequently, the second and third cover pieces 10b and 10c can move to the left from the state of FIG. 3A until the stoppers 12 thereon abut their corresponding rubber cushions 11. Thus, the telescopic cover 1 can be extended to the state shown in FIG. 3B. Furthermore, the wipers 13 serve to wipe off chips and other substances adhering to the upper surfaces of the insert-side cover pieces 10b and 10c, thereby preventing their penetration into gaps between the cover pieces. In general, the stoppers (or rubber cushions) and the wipers are integrally formed or the wipers may be designed to be used as the stoppers (or rubber cushions) (see Japanese Patent Application Laid-Open No. 7-60593).
Moreover, FIGS. 4A and 4B are views showing an example of the extension/retraction limiting mechanism in which stoppers 12 and rubber cushions 11 are provided on side surfaces of cover pieces of a telescopic cover 1. Except for the arrangement of the stoppers 12 and the rubber cushions 11 are provided on the cover side surfaces, this example is substantially identical to the example shown in FIGS. 3A and 3B in which the extension/retraction limiting mechanism is provided on the top plates of the cover pieces. Furthermore, also in this case, the positions of the wipers and the stoppers (or rubber cushions) are generally located in line with each other.
Since the wipers are designed to wipe off chips, dust, cutting fluid and other substances adhering to the cover pieces, thereby preventing penetration of the substances into gaps between the cover pieces, they must be provided on the distal end portions of the cover pieces. Therefore, if the wipers and the stoppers are integral with one another (or if the wipers are also used as the stoppers), the arrangement positions of the stoppers are very limited. Moreover, the telescopic cover should follow rapid axial movement and the stoppers and the wipers (buffer members) collide with one another, so that an impact is produced between the cover pieces. Thus, the stoppers and the rubber cushions are components that require periodic maintenance management work. If the stoppers (or rubber cushions) and the wipers are integral with one another, the wipers must also be replaced when the stoppers are replaced, resulting in problematic maintainability.
Moreover, if an attempt is made to form a telescopic cover with the stoppers (or rubber cushions) and the wipers integral with one another, the arrangement positions of the stoppers are limited, so that it is difficult to change the design to make these components compact. Furthermore, as for the structures in which the components are provided on the side surfaces of the cover pieces, the wipers and the stoppers (or rubber cushions) are generally fixed in line with each other. Since the wipers must always be in contact with the cover pieces to close the gaps between the cover pieces, the arrangement positions of the wipers affect the amount of extension and retraction of the telescopic cover as well as the cover stroke.